Tuning a hearing-enhancement device to fit a particular subject is typically costly and time consuming, both for a hearing-impaired subject and an audiologist. Using conventional techniques, it is often extremely difficult for the audiologist to manually tune the large number of parameters that usually must be set if the hearing-enhancement device is to perform optimally. As a result, even after considerable expenditure of time and money, a subject may not benefit from a hearing-enhancement device or system.
Typical of difficulties inherent in tuning a digital hearing device are the difficulties often encountered in tuning a cochlear implant. Once such a system is implanted, as with many other types of digital hearing-enhancement systems, a suitable speech coding and mapping strategy must be selected to optimize the performance of the system for day-to-day operation. The mapping strategy pertains to an adjustment of parameters corresponding to one or more independent channels of a multi-channel cochlear implant or other hearing-enhancement system. Selection of a strategy typically occurs over an introductory period of approximately six or seven weeks, during which the hearing-enhancement system is tuned for the particular subject. During this tuning period, users of such systems are asked to provide feedback on how they feel the device is performing.
More particularly, to create a mapping for a speech processor, an audiologist first determines the electrical dynamic range for each electrode or sensor used. The programming system delivers an electrical current through the hearing-enhancement system to each electrode in order to obtain the electrical threshold (T-level) and comfort or “max” level (C-level) measures defined by a system's manufacturer. T-level or minimum stimulation level is the softest electrical current capable of producing an auditory sensation in the subject 100 percent of the time. The C-level is the loudest level of signal to which a subject can listen comfortably for a long period of time.
A speech processor is then programmed or “mapped” using one of several encoding strategies so that the electrical current delivered to the implant will be within this measured dynamic range, i.e., between the T- and C-levels. After T- and C-levels are established and the mapping is created, the microphone is activated so that the subject is able to hear speech and other sounds. From that point onwards the tuning process continues as a traditional hearing test. Hearing-enhancement device users are asked to listen to tones of varying frequencies and amplitudes. The gain of each channel can be further altered within the established threshold ranges such that the subject is able to hear various tones of varying amplitudes and frequencies reasonably well.
Thus, as already noted, fitting and tuning a hearing-enhancement system of any type so as to meet the needs of a particular subject is typically quite costly and very time consuming, both from the perspective of the hearing-impaired subject and the audiologist. The functions of such a system are regulated by a large number of parameters, values for each of which must be determined so as to tune the system to provide optimal performance for the particular subject. In order to do so, the subject has to be thoroughly tested with respect to each set of parameter values. The number of tests increases exponentially as the number of system parameters increases.